A wide variety of different types of communication cables are utilized to transmit information. For example, twisted pair communication cables are utilized to transmit Ethernet and other signals. As desire for enhanced communication bandwidth presses transmission media to convey information faster and more efficiently, communication cables are also required to maintain signal fidelity, avoid crosstalk, and satisfy other electrical performance criteria. The market further expects cost reduction to accompany advances in performance.
Communication cables are often deployed in applications involving fire performance considerations. For example, cables intended for installation in a plenum space typically must satisfy burn and smoke performance standards. The materials utilized for twisted pair insulation affect both the electrical performance and the fire performance of the twisted pair. Conventional materials offering improved electrical and fire performance typically impose higher costs. Accordingly, cable designers face challenges with achieving high electrical and flame performance objectives on the one hand and with meeting economic constraints on the other hand.
Fluoropolymers are often used as insulation material for high performance copper data cables that are specifically designed for plenum flame/smoke ratings. The desirable electrical characteristics of fluoropolymers generally provide low dielectric and dissipation properties, and most fluoropolymers further exhibit good flame/smoke properties when subjected to industry standard flame tests. Fluoropolymers, however, are often prohibitively expensive and are frequently in short supply. For example, fluorinated ethylene propylene (“FEP”) offers desirable levels of electrical and fire performance, but is typically expensive and can be subject to supply shortages.
In order to reduce the cost of plenum-rated cables, attempts have been made to incorporate less costly flame retardant insulation materials into the cables. For example, plenum cables have been developed in which a portion of the twisted pairs utilize FEP insulation while the other twisted pairs utilize a flame retardant polyolefin insulation. While these cable constructions reduce the amount of FEP, they do not eliminate the use of FEP. Attempts have been made to replace FEP with flame retardant polyolefin compounds. However, the flame retardant polyolefin compounds have relatively worse electrical performance than FEP and non-flame retardant polyolefin compounds. This reduced performance has the potential to reduce the velocity of signal propagation along insulated conductors, thereby resulting in increased signal time delays that may fail to satisfy electrical performance requirements. Accordingly, an opportunity exist for improved plenum-rated communication cables that utilize flame retardant polyolefin insulation.